Smoking tobacco and/or smoking tobacco mixed with cannabis might lead to worse physical health outcomes than smoking cannabis on its own, according to a San Francisco Chronicle blog quoting an Australian study.

Researchers at the University of New South Wales, Sydney, Australia, recruited 350 adults over the age of 40 and divided them into four groups: cannabis-only users, tobacco+cannabis users, tobacco-only users, and a control group of abstainers.

The population size was small, but the authors concluded in a report published in the journal Addictive Behaviors that the control and cannabis-only groups tended to report the best health, while the two tobacco-smoking groups fared the worst.

All three smoking groups reported significantly higher rates of emphysema than did the control group. But all members of the cannabis-only group diagnosed with the debilitating lung disease had formerly been regular tobacco smokers.